Method for making a tubular element



April 15, 1958 n-E 2,830,363

METHOD FOR MAKING A TUBULAR ELEMENT Filed April 15, 1954 3 Sheets-Sheet l INVENTOR. GEORGE R. REITER B ms ATTORNEY April 15, 5 G. R. REITER 2,830,363

METHOD FOR MAKING. A TUBULAR ELEMENT Filed April 15, 1954 3 Sheets-Sheet 2 INVENTOR. GEORGE R. REITER BYZQI HIS ATTORNEY April 15, 1958 c R REITER 2,830,363

METHOD FOR MAKING A TUBULAR ELEMENT I Filed April 15, 1954 I 5 Sheets-Sheet 3 FIG. 1 v

INVENTOR.

GEORGE R. REITER BY g I r HIS ATTORNEY tion of the inner wall of the suction tube.

. 2,830,363 Patented Apr. 15, 1958 METHOD FOR MAKING A TUBULAR ELEME George R. Reiter, North East, Pa., assignor to General Electric Company, a corporation of New York Application April 15, 1954, Serial No. 423,345

2 Claims. (Cl. 29-517 This invention relates to a method and apparatus for making a tubular element which consists of a spiral or curved member, such as a wire or tube, disposed in a tubular member.

This invention has many applications, such as to provide a heat exchanger; a vibration damper for tubes; 2. pump element of the Archimedes screw-type; a coaxial cable, etc. While this invention thus has many applications, it will be described herein as applied to a bitubular heat exchanger for use in a refrigeration system.

It is desirable in refrigeration systems to place the capillary restriction in heat exchange relation with the suction line since this increases the efiiciency of the refrigeration system. This has been accomplished heretofore by wrapping the capillary tube about the outside of the suction line or placing the capillary tube in metal bond contact with the suction line. However, these arrangements are expensive and unless carefully constructed may not provide the desired heat exchange relation between the elements. v

The present invention provides an improved heat exchanger particularly adapted to provide heat exchange relation between the suction line of a refrigeration system and the capillary tube. Not only does the present invention contemplate disposing the capillary tube inside of the suction line, but it also embodies the idea of insuring that the capillary tube is always in contact with some por- This is accomplished by the method and apparatus of the present invention.

By placing a spiral or curved capillary tube incontact with the inner wall or surface of the suction tube along all points of the capillary tube, the amount of heat exchange is increased since there is not only heat exchange relation between the capillary tube and the fluid flowing through the suction line but there is also heat exchange between the capillary tube and the suction tube, the latter being metal-to-fluid-to-metal heat exchange due to a film of oil building up between the capillary tube and the suction tube from the oil'that is in the refrigeration system. This produces a more efiicient heat exchanger.

It will be understood, of course, that this particular type of heat exchanger wherein a curved tube is disposed inside of a straight tube could be employed in situations other than a refrigeration system. It results in giving not only fluid-to-metal heat exchange, which normally results from placing a tube inside of a second tube through which fluid flows, but also metal-to-fluid-to-metal heat exchange.

A primary object of the present invention is to provide a more efficient heat exchanger.

Another object of the invention is to provide a spiral become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of this invention, the method thereof for forming a spiral member inside of a straight tubular member comprises the steps of placing. a first straight member inside of a second straight tubular member, curving both members while thus assembled in a predetermined way, and the straightening of the assembly which straightens the second member and leaves the first permanently curved within the second.

There is also provided apparatus for forming a curved member inside a straight hollow member including means to dispose a first longitudinal member inside a second,

Fig. 2 is an elevation view partly in section of a modified form of apparatus; v

Fig. 3 is an elevation view partly in section of the partial straightening step of the apparatus shown in Fig. 2;

Fig. 4 is an elevation view partly in section of the complete straightening step of the apparatus shown in Fig. 2; Fig. 5 is an elevation view of another form of apparatus for making the heat exchanger;

Fig. 6 is an elevation view similar to Fig. 5 showing the parts in operative position;

Fig. 7 is a plan view of the apparatus shown in Fig. 5;

and

Fig. 8 is a plan view similarto in operative position.

Referring to the drawings and particularly Fig. 1, one embodiment of apparatus constructed in accordancewith this invention comprises a first set of rollers 2 and a second set of rollers 3 spaced from the first set of rollers 2. These rollers coact to make a bi-tubular element comprising a tubular member 5 having disposed therein a second tubular heat exchange member 6. The rollers of the first set of rollers 2 are so disposed with respect to each other that they will bend or curve the longitudinal hollow straight member 5 and the straight member 6 inserted in the member 5 as the combination is passed through the rollers. The first set of rollers curves or bends members 5 and 6 to such an extent that they are both deformed. It will be understood that the inner member 6 Fig. 7 showing the parts is disposed inside of the outer member 5 prior to passing I first set of rollers 2, then pass through the second set ofv rollers 3, which are designed tto straighten the outer member 5. The roller 2a of the first set of rollers 2 is disposed in a different plane than the plane of the other rollers of the set to prevent the members 5 and 6 from circling back into their own feed path to the rollers 2 and to aid in spiraling the members 5 and 6 toward the second set of rollers 3. The first set of rollers 2 form the members 5 and 6 in a shape corresponding to a cylin drical spiral. The second set of rollers 3 is in a plane at an angle to the plane of the first set of rollers so that the members 5 and 6 will spiral into the second set of rollers 3. The position and angle of rollers 3 depend on the mechanical tightness-and angle of rollers 2 and 2a. The exact angular relationships are not important provided the end of the spiraling tube enters rollers 3 The inner member 6, which has been-1 deformed, as previously stated, by the first set of rollers 2, retains at least-part of itscurvature while passing through the second set of rollers 3 since the outer diameter of inner member 6 is less than the inner diameter of outer member-- sotthat the second set of rollers 1 3 cannot directly exert a positive displacement on the inner member 6 to straighten itw After passing through the second set of rollers-i3; theouter member 5' isagain straight while the -inner-member-6 is-curvedL The/inner member 6 is socurvedyb'y the-setof rollers 2 that it is in contact at all points withtheinside wall of theouter member or membersi: and 6*aboutthemandrel 10, the membersS and 6*are curved or' deformed in the form of a cylindrical spiral. It is then necessary tostraighten'the outer member 5 to provide the desired heat exchanger. Suitableforce applied. lengthwise of the spiral or in other wordsparallel'tothe axis thereof, as indicated by the arrows in Figs. 3 and 4, may be applied to members 11 attached to each end of the outer member 5. The force required to straighten the'outer member may be applied in two straightening operations, as shown in Figs. 3 and 4, or ina single straightening operation, if desired. At the completion of'the straightening step, theinner member 6'is curved'or spiraled inside of thte outer member 5 with the innermember 6 always being in contact with some portion of the inner wall of outer member 5.

Itwill be understood that the same steps are performed by the apparatus of Fig. 1 as the apparatus of Figs. 2-4. Thus, the first set of rollers 2 of Fig. 1 spirals the members Sand 6 similar to the bending of'the members 5 and6' about the mandrel 10 of Fig. 2. The second set of rollers 3 of Fig. l straightens the outer member 5 while this operation is performed in Figs. 3 and 4 by applyingforce to the members 11.

Figs. 5"to 8 disclose a third apparatus for forming a curved member inside of a straighttube. This apparatus includes a first stationary die and a pair of cooperable movable dies 21 and 22 and a second stationary die 23 and a pair of cooperable movable dies 24 and 25. The stationary die 20 has an opening 26 through which the members 5 and 6 are fed into the stationary die. It will beunderstood that the inner member6 has been disposed inside theouter member 5 prior to, passing. intoithe opening 26. When the members 5 and 6 pass throughfthe stationary diea20, the movable die 22 and thendie 21 are moved toward each other and toward the stationary die to, impart a discontinuous curved or,substantially sinusoidal shape to the inner and outer members or tubes. The members 5 and 6 then index the distance A in the first stationarydie 20.and. when the 1 dienext closes the curved portion of the outer member 5 is straightened, the inner member6 is partially straightened butremains curved since its outer diameter is less than theinner diameter of outer member 5 so that the dies cannot completely straighten member, 6.

To insure that the outer member 5 is straight before beingactedupon by the, second set of dies the members 5 and 6 pass through an opening 28 inthe stationary die 23. The movable die.25, and then die 24 are'moved toward each other and toward the stationary die 23 to bend the, inner and outer members to a discontinuous curved or substantially sinusoidal shape. However, it will beobserved that the second bending occurs at right angles. -to..the plane-,of the original bend since the plane of ,the-,second stationary die 23 anddtsmovableudies is 7 4 atrighfangles to the plane containing the first stationary die 20 and its movable dies. The peaks of the second curve on sinusoid falhhalfway between-the peaks of the first curve or sinusoid on the member 5. The members 5 and 6 then index the distance A to pass to the second section of the second stationary die where the outer member 5 is-restraightened similar to the operation in the first stationary die 20. However, the combination of the two sinusoid curves is still imparted to the inner 7 member 6' so that the'inner member 6 is in substantial contact with the inner wall of outer member 5 along the entirelength of the inner member 6. It will be understood that the'sinusoid bends could be'performedmanually rather than in 'apress,'if desired.

The present invention may be employed not only to form a heat exchanger having a spiral or curved member inside of a tubular member but also may be employed anywhere that it is desired to form a spiral member inside of a tubular member. For example, an effective vibration dam er for atube"'may be constructed byspiraling a wire orsma1l 't'ubeinside'an outside tube by thisinvention; Similarly, a pump element of the Archimedes screw-type may be produced by'spirally locatinglatube or wire inside a tube. Another use may be to'form a' coaxial cable byspiraling a central conductor with spaced insul'ations inside of an outer tube so that the springback' of the conductor. holds the insulators in place. It willbe obvious that the method and apparatus ofthis invention may be employed to form other similar suitable devices.

The. present invention' has'the advantage of eliminating one'exposed tube in -a refrigerator since the capillary tube isdisposed inside the suction tube. It also will be understood'that the spring of the inner member against the outer member may be sufiicient to permit the inner member to remain incontact with the outer member even though the outerdrnember is: later curved or bent to be guidedaroundobstructions or to conform to manufacturing practice.

It should be understood that the completed apparatus. including the generally spiraled inner member could be'shaped into acurved or looped configuration for heat exchangepurposes and, in fact, can be left in that combination merely through terminating the straightening step somewhatshort of a completely straight outer member or tube.

While the present invention has been described by reference to a particular embodiment thereof, it will be understood that modifications may be made by those skilled in theart without actually departing from the invention... I, therefore; aim in the appended claims to covertall such variations as'come within the true spirit and scope of the --foregoing disclosure.

Iblaim:

l l; The method of producing anarticle' ofmanufacture comprising a substantially straight tubular member havingithereina spiralled tubular member'of smaller diameter than said straight member which comprises the steps of-p1acing. a first straight tubularmember loosely inside a second straighttubular member, bending the assembly of; said members into the form of a cylindrical spiral and=thereafter applying a straightening force to said second tubular member sufficient to substantially straighten.

' the second tubular'member, said straighteningoperation substantially straight second'tubular member and in contact "with portions I of said second member.

2. The method of claim"l in which'the straightening forcebis" applied in a direction-substantially parallel to the axis of said cylindrical spiral.

(References ou following page) References Cited in the file of this patent UNITED STATES PATENTS Prime Oct. 20, 1914 Priest Jan. 14, 1930 5 Lawson Nov. 28, 1933 6 Stone Dec. 16, 1947 Anderson Apr. 18, 1950 Heller Aug. 1, 1950 Reed Sept. 14, 1954 Collins Feb. 21, 1956 

